The present invention relates to a tuning fork resonator device and, more particularly, to an assembly of the tuning fork resonator device which is less susceptible to an external impact or shock applied to the device.
The tuning fork resonator device is generally used in an oscillator in which the natural frequency of the tuning fork is converted into an electrical signal which is fed back to the tuning fork for the continual oscillation of the tuning fork, or it is used in an filter in which the tuning fork, among all the incoming signals, resonates in response to a particular signal having a frequency equal to the natural frequency of the tuning fork for filtering only the particular signal therethrough.
One conventional tuning fork resonator device is shown in FIG. 1. The conventional tuning fork resonator device of FIG. 1 includes a U-shaped tuning fork 1 made of a hard metal such as an Elinvar and having a base portion 1c and two arms 1a and 1b extending parallel to each other from the base portion 1c. The tuning fork 1 is supported on a substrate 4 by a supporting pin 3 projecting directly from the substrate 4. Piezoelectric elements 2a and 2b are electrically connected to terminal pins 5 and 6 through respective lead wires and are respectively deposited on the side surface of the arms 2a and 2b.
Although the tuning fork resonator device of FIG. 1 has a compact size with a simple structure, an external impact or shock applied to the casing 7 or substrate 4 is directly transmitted to the tuning fork 1 since the support pin 3 is directly connected to the substrate 4 and has a considerably short length for positioning the tuning fork 1 as close as possible to substrate 4. Thus, an undesirable shock noise is generated from the tuning fork 1. Therefore, the tuning fork resonator device of FIG. 1 can not be used at places where the shocks or impacts are often produced, for example, in the vehicle or near audio devices.
For the purpose of absorbing the shock, there has been proposed a tuning fork resonator device of FIGS. 2(a) and 2(b) including a U-shaped support member 8 having the ends affixed to the T-shaped terminal member 3. The U-shaped support member 8 has a tongue 8a extending from its base portion parallelly to the arms of the member 8. The end portion of the tongue 8a lies over a rubber damper 9 mounted on the base 4. The U-shaped support member 8 further has a projection 8b extending upwardly from a position adjacent to the tongue 8a for supporting the base portion 1c of the U-shaped tuning fork 1. According to this structure, a large shock or impact applied to the tuning fork resonator device can be absorbed by the resiliency of the long support member 8 and by the damper 9. However, it has been found that small impacts are not as effectively absorbed as the large impacts.
Another conventional tuning fork resonator device is shown in FIGS. 3(a) and 3(b) including a cubic rubber 11 surrounded and held in position by a frame 4a installed on the substrate 4 and a bar 10 made of Elinvar and inserted into an opening formed in the cubic rubber 11 for supporting a pair of vibrating arms 1a and 1b attached to the bar 10 by a brazing method. For electrically connecting the tuning fork with the terminal pin 3, a lead wire 15 is extended between the terminal pin 3 and the bar 10. The employment of the lead wire 15 increases the steps of the soldering process during the manufacture of the device. Additionally, since the bar 10 is made of an Elinvar, it is difficult to deposite solder beads on the bar 10. Therefore, it is necessary to use a special solder to solder the lead wire 15 onto the bar 10, thus complicating the manufacturing steps. Furthermore, since the wire 15 extends almost tightly between the bar 10 and the pin 3, the wire 15 may be forcibly cut by the applied impacts.
Moreover, since the bar 10 extends vertically from the substrate 4 with one end portion supported by the rubber damper 11 and the other end portion supporting the vibrating arms 1a and 1b, the height of the tuning fork resonator device is considerably high.
FIGS. 4(a) and 4(b) show a further conventional tuning fork resonator device having a pair of walls 13 and 14 each carrying a rubber plate 11 in such a manner as to define a predetermined gap between the rubber plates 11. The base portion of the tuning fork, that is, where the vibrating arms 1a and 1b are held together by a spacer 12 made of Elinvar is tightly held in the gap between the rubber plates 11. To ensure that the base portion of the tuning fork is held between the rubber plates 11, the contacting surface between the base portion and the rubber plates has to be considerably large in area or the tuning fork may easily be removed from its proper position. Therefore, in addition to above mentioned disadvantages, the tuning fork resonator device of FIGS. 4(a) and 4(b) has the disadvantage that its size in the longitudinal direction is considerably large.